G'day,
yes, i´m sure the 49920 is discontinued; we´ve touched on this in several posts some months ago. And that´s one reason as to why there are so many units with deeply discounted prices in the grey market.
The other models are higher/larger, not the least due to the improved pressure resistance of 1.000m/3.000m.
Such requires an even more massive case and thicker crystal, therefore the case got wider and higher!
In addition, at least the 1.000m Sea Hawk model features a manufacture-made casework, which is quite some efforts to produce.
But the movements are almost unchanged towards the "John Harrison" variant of the Sea Hawk II.
I´d still recommend to see any piece in consideration up close.
The steel units ones aren´t for everyone qnd quite substantial - the "Sea Hawk 1.000m" even more. The "Sea Hawk Pro" is a real beastie (a wearable one, though)!
I´m sure your GP dealer will try to help; usually pieces not in stock can be ordered from the regional distribution. At least that may be worth a try, as the 49920 is discontinued not very long ago and there still may be some left.
Cheers,
Peter